Turbine ring

ABSTRACT

A turbine ring made up of an assembly of a plurality of sectors forming the outer shroud of the rotor of said turbine. The sectors are united end to end with interposed sealing systems comprising tongues housed in slots, said tongues being rectilinear and engaged in respective rectilinear slots in the radial faces of said sectors.

The invention relates to a turbine ring forming the outer shroud of therotor of said turbine. The invention applies particularly to a highpressure turbine situated immediately downstream from the combustionchamber of an airplane turbojet. It relates more particularly to theinterconnection and cooling of the sectors making up said turbine ring.

BACKGROUND OF THE INVENTION

In a turbine of the kind mentioned above, driven by gas at very hightemperature, the rotor rotates inside a stationary turbine ringconstituted by a plurality of curved sectors that are united end to endcircumferentially in order to form the rotor shroud. The temperature ofthe gas driving the blade wheel is such that the thermomechanicalstresses that are created between the sectors can lead to deterioration,reducing the lifetime of such rings. Typically, small cracks and/orflaking can often be observed on the inside (or “hot”) face of thesectors, mainly in the vicinity of the connections between adjacentsectors.

To provide the ring with better sealing, reducing leaks of non-workingair, and in order to prevent hot gas being reinserted, sealing systemsare provided between such adjacent sectors, said systems comprisingtongues that extend between the sectors and that are received in slotsformed facing them in the adjacent radial faces of said sectors.

For example, a prior art sector 1 shown in FIG. 1 includes a sealingsystem comprising four tongues 2-5 received in slots 6, 7, and 8. Thetongue 3 is bent and extends between two slots 6 and 7 that open outinto each other and that receive the other tongues 2 and 4 which arestraight. It is difficult to machine the slots accurately, in particularbecause of the difference in thickness needed to be able to insert thebent tongue. It is difficult to position this tongue properly. Inaddition, the tongue 2 is received entirely within a slot 6 that isparallel to the hot face 9 of the sector and that is close thereto.Unfortunately, the mere fact of forming the slot leads to stressconcentration zones which, when situated close to a hot surface, weakenthe part and accelerate deterioration thereof. The invention makes itpossible to eliminate these drawbacks, in particular.

OBJECTS AND SUMMARY OF THE INVENTION

The invention thus provides firstly a turbine ring forming a rotorshroud, the ring being of the type constituted by a plurality of sectorsinterconnected end to end with interposed sealing systems comprisingtongues extending between adjacent sectors, said tongues being housed inslots formed facing each other in adjacent radial faces of said sectors,wherein each sealing system is constituted by rectilinear tonguesengaged in respective rectilinear slots in said radial faces.

The fact of making the sealing system from tongues that are straightsimplifies making the slots and facilitates mounting the tonguestherein. In addition, control over the positioning of the tongues isimproved because of the bear against surfaces that are under bettercontrol since they are strictly linear. Overall, leakage sections aremade smaller. A configuration with only three tongues is describedbelow.

More particularly and advantageously, in the above-defined turbine ring,each sealing system comprises a first tongue and a second tongueextending in a chevron configuration on the inside of said radial faces,said tongues being engaged in rectilinear slots of said radial facesdefining their relative positions accurately. As a result, air leakagebetween two consecutive sectors can be accurately calibrated. Suchleakage can thus be identical through all of the inter-sector spaces.Overall, it is estimated that the leakage rate can be reduced by 10% to20% compared with the above-described prior art configuration.

Another advantage of the invention lies in the fact that arranging thetongues in a chevron configuration on the hot face side makes itpossible both to move the stress concentration zones further away fromsaid hot face (since the slots go away therefrom), and also to providesufficient space between the tongues and the hot face to allow coolingair ejection channels to open out therein, which channels are fed from acavity formed within the sector itself.

More precisely, the invention also provides a turbine ring as definedabove in which each sector includes a cooling air flow cavity, the ringfurther including air ejection channels extending between said cavityand at least one radial face of the sector, these channels opening outin said radial face between an inner edge thereof and said first andsecond tongues.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and other advantages thereofwill appear more clearly in the light of the following description givenpurely by way of example and made with reference to the accompanyingdrawings, in which:

FIG. 1 shows a radial face of a sector used in building up a prior artturbine ring;

FIG. 2 shows a radial face of a sector used in building up a tongue ringin accordance with the invention;

FIG. 3 is a diagrammatic view showing two consecutive sectors seenlooking along III in FIG. 2;

FIG. 4 is a diagrammatic view of the casing associated with such ringsectors;

FIG. 5 is a diagrammatic view showing the various possible orientationsfor said first and second tongues; and

FIGS. 6 to 8 are fragmentary views showing variants of one of thesectors shown in FIG. 3.

MORE DETAILED DESCRIPTION

In the drawings, and more particularly in FIGS. 2 to 4, there can beseen turbine ring sectors 11 constituting the stationary shroud of arotor (not shown), specifically a rotor in the high pressure turbine ofa turbojet. This turbine is located downstream from the combustionchamber. Specifically, such a ring is made up of thirty-two curved ringsectors 11 such as those shown, disposed end to end to form a slightlyconical shroud surrounding said rotor. Each sector 11 is constituted bya slightly curved thick plate so as to build up the ring. There is asubstantially rectangular inside face 12 that is slightly concave andthat is referred to as the “hot” face since it comes into contact withthe stream of hot gas, and a substantially rectangular outer face 14referred to as the “cold” face. Relative to the flow direction of hotgas passing through the rotor, there is also an inlet edge 16 facing thecombustion chamber nozzle, and an opposite outlet edge 18. Each sector11 also has two radial faces 20 and 21 via which it is connectedcircumferentially to the adjacent sectors via sealing systems 26 (seeFIG. 2) as mentioned above. Each sealing system 26 is constituted by aset of tongues engaged in corresponding slots defined in said facingradial faces 20, 21. Each tongue is engaged in two slots belonging totwo circumferentially-adjacent ring sectors.

The tips of the rotor blades travel past the inner surface of the ringas constituted in this way. The direction of rotation is represented byarrow F in FIG. 3. The hot gas expelled from the combustion chamber thusflows close to the inside surface of the ring, which must thereforewithstand very high temperatures. It is therefore necessary both tominimize temperature gradient within the structure of the ring as muchas possible (thereby minimizing in particular leakages of gas betweenthe sectors), and also to cool said ring effectively. For this purpose,use is made of a fraction of the air delivered by the compressor feedingthe combustion chamber. To do this, each sector 11 is hollow andincludes a cooling air flow cavity 35 fed from the outside.

FIG. 4 is a highly diagrammatic view showing the position of the ringmade up from the set of sectors 11. A turbine casing 15 co-operates withthe ring to define an annular cavity 17. The assembly extends radiallyoutside the high pressure bladed wheel 19, itself interposed axiallybetween the high pressure nozzle 21 and the low pressure nozzle 23. Aircoming from the compressor is taken from a point upstream of thecombustion chamber and penetrates (via holes) into the annular cavity17. This cavity thus feeds all of the sectors in the ring. Each ringsector (FIG. 3) has two distinct cavities 39 and 40 of zigzag shape,separated by a partition 42, and fed via respective orifices 37 and 38.The air flowing in the cavity 39 escapes via a series of ejectionchannels 44 opening out in the inlet side 16 of the ring sector, whilethe air which flows in the cavity 40 escapes via a series of ejectionchannels 44 opening out in the outlet side 18 of the ring sector.

Apart from the sealing systems between the sectors, the arrangementdescribed above is already known. The invention relates in particular toan advantageous improvement in said sealing systems between the sectors.

More particularly (FIGS. 2 to 4), each sealing system 26 is constitutedin this case by three rectilinear tongues engaged in respectiverectilinear slots in the radial faces of two adjacent sectors.Specifically, each sealing system (FIG. 2) comprises a first tongue 27and a second tongue 28 situated on the insides of said radial faces,i.e. beside the hot faces of the sectors. The tongues 27 and 28 arearranged in a chevron configuration, i.e. they are engaged in slots 31and 32 in said radial faces that extend at an angle relative to theinner and outer faces 12 and 14 of the sectors. These slots define therelative positions of the two tongues.

In addition, each sealing system includes a third tongue 29 extendingsubstantially from one end to the other of the adjacent sectors,parallel to the axis of the ring and on the outer side of said radialfaces. The tongue 29 is engaged in rectilinear slots 33 in the adjacentsectors. As can be seen in FIG. 2, the first tongue 27 extends between apoint A situated close to the inlet side of the two sectors close to theinside (i.e. close to the hot faces) and a point B situated close to thethird tongue 29. The second tongue 28 is positioned so as to extendbetween a point C situated close to the outlet side 18 of each of thesectors close to the inside and a point D situated close to the firsttongue, substantially between the middle and a two-thirds pointtherealong starting from point A.

The pressures which become established in the spaces between the sectorson the inside and on the outside, and also between the third tongue andsaid first and second tongues taken together are such that said firstand third tongues 27, 29 are pressed against the inside faces of theslots 31, 33 in which they are received, while said second tongue 28 ispressed against the outside faces of the slots 32 in which it isreceived, as can be seen in FIG. 2.

The length of the first tongue 27 depends on the angle it makes with thefirst tongue 29. Once this angle has been determined (severalpossibilities are shown in FIG. 5), the position and the length of thesecond tongue can be derived therefrom.

The angle defined between the first and third tongues may lie in therange 15° to 70°, approximately.

The slots can be machined accurately and they are well located. Thetongues can be inserted in these slots and their relative positions canbe well controlled. As a result the leakage section between said firstand second tongues (at S₁) and the leakage section between the first andthird tongues (at S₂) are well controlled.

With reference more particularly to FIGS. 2 and 3, another advantageousfeature of the invention can be seen concerning the cooling of theradial faces 20 and 21 with air from the cooling air flow cavity 35. Itcan be seen that each sector has air ejection channels 50 extendingbetween the cavity 40 and at least one radial face of the sector. Thesechannels open out in the radial face 20 between its inside edge (hotface) and said first and second tongues 27, 28. The chevronconfiguration of these two tongues leaves room to form these airejection channels. These channels are disposed in a row parallel to theaxis of the ring. In the example of FIG. 3, they all extendperpendicularly to the radial face. In the example of FIG. 6, some ofthe channels 50 extend perpendicularly to the radial face while otherssituated at the ends of said row, or at least one of them, are at anangle diverging from the others, on going from the cavity towards theradial face. The angle between the diverging channels may lie in therange 10° to 120°. In certain circumstances, channels could be providedat angles that converge in the opposite direction. In the variant ofFIG. 7, the channels are parallel and form an angle relative to adirection perpendicular to the radial face. The angle is such that theair is ejected with a component directed towards the rear of the ring.In the variant of FIG. 8, the channels are parallel and make an anglerelative to a direction perpendicular to the radial face. The angle issuch that the air is ejected with a component directed towards the frontof the ring.

In the example, the channels 50 open out it the radial face 20 that isthe first face to be reached by the blades, given the direction ofrotation represented by arrow F. This is favorable for avoiding orlimiting any reintroduction of hot gas into the inter-sector spaces. Itwould also be possible to make similar channels through the oppositewall, opening out in the radial face 21. The air escaping from thechannels 50 cools the wall through which they are formed by convection(thermopumping), while the opposite wall (face 21) is cooled by theimpact of the jets of air. In addition, the jets of air escaping fromthe channels 50 set up a kind of fluidic system preventing hot gas beingingested.

It should also be observed that the slots 31, 32, and 33 are preferablyindependent, i.e. they do not communicate with one another. This avoidsany need to make any tool clearance at the junction between two slots.Leakage sections between the sectors are also reduced.

The invention also provides any ring sector or any assembly of ringsectors presenting the characteristics described above.

1. (canceled)
 2. A turbine ring according to claim 17, wherein eachsealing system between two sectors comprises first and second tonguesextending in a chevron configuration from the insides of said radialfaces, said tongues being engaged in slots in said radial faces definingtheir relative positions.
 3. A turbine ring according to claim 2,wherein each sealing system includes a third tongue extendingsubstantially from one end to the other of the adjacent sectors,parallel to the axis of the ring, and on the outside of said radialfaces.
 4. A turbine ring according to claim 3, wherein said first tongueextends between a point situated close to an inlet edge of each sector,towards the inside, and a point situated close to said third tongue. 5.A turbine ring according to claim 4, wherein the angle defined by thedirections of said first and third tongues lies in the range 15° to 70°.6. A turbine ring forming a rotor shroud, the ring comprising aplurality of sectors interconnected end to end with interposed sealingsystems comprising tongues extending between adjacent sectors, saidtongues being housed in slots formed facing each other in adjacentradial faces of said sectors, wherein each sealing system includesrectilinear tongues engaged in respective rectilinear slots in saidradial faces, and wherein the slots formed in each radial face areindependent such that said slots do not communicate with each other,wherein each sealing system between two sectors comprises first andsecond tongues extending in a chevron configuration from the insides ofsaid radial faces, said tongues being engaged in slots in said radialfaces defining their relative positions; and wherein said second tongueextends from a first end point situated close to an outlet edge of eachsector, towards the inside, to a second end point situated close to saidfirst tongue, said second end point being substantially between themiddle of said first tongue and a two-thirds point starting from an endpoint of said first tongue close to an inside face of said sector.
 7. Aturbine ring forming a rotor shroud, the ring comprising a plurality ofsectors interconnected end to end with interposed sealing systemscomprising tongues extending between adjacent sectors, said tonguesbeing housed in slots formed facing each other in adjacent radial facesof said sectors, wherein each sealing system includes rectilineartongues engaged in respective rectilinear slots in said radial faces,and wherein the slots formed in each radial face are independent,wherein each sector includes a cooling air flow cavity, wherein eachsector includes air ejection channels extending between said cavity andat least one radial face of said sector, said channels opening out insaid radial face between an inside edge thereof and said first andsecond tongues.
 8. A turbine ring according to claim 7, wherein at leastsome of the channels extend substantially perpendicularly to said radialface.
 9. A turbine ring according to claim 7, wherein the orifices ofsaid channels are disposed in a row parallel to the axis of the ring.10. A turbine ring according to claim 9, wherein channels situated atthe ends of said row are formed at an angle and diverge relative to theother channels on going from the cavity towards the radial face.
 11. Aturbine ring according to claim 17, wherein the facing slots of twoadjacent radial faces of said sectors house a single tongue.
 12. Aturbine, including a ring according to claim
 17. 13. A turbine ringaccording to claim 7, wherein each sealing system between two sectorscomprises first and second tongues extending in a chevron configurationfrom the insides of said radial faces, said tongues being engaged inslots in said radial faces defining their relative positions.
 14. Aturbine ring according to claim 13, wherein each sealing system includesa third tongue extending substantially from one end to the other of theadjacent sectors, parallel to the axis of the ring, and on the outsideof said radial faces.
 15. A turbine ring according to claim 14, whereinsaid first tongue extends between a point situated close to an inletedge of each sector, towards the inside, and a point situated close tosaid third tongue.
 16. A turbine ring according to claim 6, wherein eachsector having an inside face in contact with a stream of hot gas.
 17. Aturbine ring forming a rotor shroud, the ring comprising a plurality ofsectors, each sector having an inside face in contact with a stream ofhot gas, said sectors being interconnected end to end with interposedsealing systems comprising tongues extending between adjacent sectors,said tongues being housed in slots formed facing each other in adjacentradial faces of said sectors, wherein each sealing system includesrectilinear tongues engaged in respective rectilinear slots in saidradial faces, and wherein the slots formed in each radial face areindependent such that said slots do not communicate with each other,wherein each sealing system between two sectors comprises first andsecond tongues, and wherein said second tongue extends from a first endpoint situated close to an outlet edge of each sector, towards theinside, to a second end point situated close to said first tongue, saidsecond end point being substantially between the middle of said firsttongue and a two-thirds point starting from an end point of said firsttongue close to an inside face of said sector.
 18. A turbine ringaccording to claim 17, wherein said first and second tongues extend in achevron configuration from the insides of said radial faces, saidtongues being engaged in slots in said radial faces defining theirrelative positions.
 19. A turbine ring according to claim 17, whereineach sector comprises an outer face, opposed said inside face, whereinsaid tongues are between said inner and outer faces.
 20. A turbine ringaccording to claim 19, wherein each sealing system between two sectorscomprises first, second and third tongues, said third tongue extendingsubstantially parallel to said outer face, and said first and secondtongues being located between said third tongue and said inner face.